Spike particles that protrude outwards?
In the Particle Properties tab check the box next to Advanced. After that it is possible to check the box next to Rotation. Under Rotation choose Normal-Tangent as the Orientation Axis.

Make sure to rotate the spike object in Edit Mode to get the desired alignment.
And it's also helpful to put the origin of the spike object at its base. (select the face at the base in Edit Mode, press Shift + S and choose Cursor to Selected. Then in Object Mode press the search key, F3 by default. Search &quot;Set Origin&quot; and choose Origin to 3D Cursor)